OpenGL - Cube display problem

Good evening,

For the school, I have to make a 3D terrain viewer editor in C++ and openGL to allow the user to create a world from cubic blocks and to navigate in it. I have already realized the cube linked to its shaders. But to allow me to have “generic” shader programs, I created different functions that don’t make my cube appear anymore. I spent several hours understanding my code line by line but I really don’t see where the problem comes from.

I leave you the image of my code, hoping that the problem appears on it.

Thanks in advance!